Modulating glymphatic clearance in Alzheimer's disease: Molecular mechanisms, imaging biomarkers, and emerging interventions.
Level 5 - mechanism / opinion, no new human data
Narrative review of mechanisms, biomarkers, and interventions without systematic review methodology or primary data
PubMed 41763274 · doi:10.1016/j.bbr.2026.116138
What was done
Narrative review summarizing experimental and human observational evidence regarding glymphatic clearance mechanisms (notably AQP4 polarization, vascular pulsatility, and meningeal lymphatics), surrogate imaging biomarkers (DTI-ALPS, perivascular space enlargement), fluid biomarkers, and emerging therapeutic approaches (sleep optimization, aerobic exercise, gamma sensory stimulation, and molecular AQP4 targets) in Alzheimer's disease.
What was found
The abstract reports no quantitative effect sizes or pooled numbers. It notes that loss of astrocytic AQP4 polarization is consistently linked to reduced CSF-ISF exchange and higher amyloid-beta and tau accumulation. Existing clinical imaging readouts (ALPS index, perivascular space enlargement) provide only indirect assessments and face intersite variability and low specificity, whereas direct contrast-enhanced MRI clearance measures remain invasive and difficult to scale.
Why it matters
Synthesizes current biological and translational frameworks connecting brain waste clearance to Alzheimer's pathology, outlining potential non-pharmacological and molecular targets for future clinical testing.
Limits
As a narrative review, it presents no primary data or systematic search protocol. Most clinical evidence relies on indirect surrogate imaging proxies rather than validated direct clearance measurements, and causal therapeutic efficacy in humans remains unproven.